An encoding detection beforehand is able to reduce the operational power losses of a practical circuitry. Prior art in this field can be categorized into two types, namely the type being applied to transform domain/quantization encoding, and the method for detecting image data to be skipped.    1. Application to transform domain/quantization encoding: detect prediction errors in advance to see if they are all zero coefficients so as to reduce the computation burden of transform coding. If the reconstruction coefficients are zero blocks, then the transform coefficients are also zero blocks, and vice versa. Under the condition of portable application, there is a great probability that the reconstruction coefficients are zero, therefore unnecessary coding computations can be avoided by using the transformation formula to derive the detection conditions for all-zero transformation coefficients. However, since transform coding is not the major source of computations, the said detection is not efficient enough to substantially reduce the computation burden of coding device.    2. Method for detecting image data to be skipped: In U.S. Pat. No. 6,396,956, there is disclosed a video coding method using image data skipping. In this method, degree of variation of an image is calculated at first, and then this variation is used to compute a variation threshold. If a sorted variation is smaller than the threshold, then an image is skipped from the reconstruction frame for the encoding block corresponding to this variation. The drawback of this method lies in that some additional calculation is needed in order to compute the block variations and some additional memory has to be allocated in order to access the block variations and arrange the variations in a decreasing or increasing order. In compared with the present invention, because the prior art technique is based on image coding, not only the detection computation is complicated, but a rough modeling may also reduce the quality of the coding.
Moreover, in U.S. Pat. No. 6,560,370, there is disclosed another video coding method using image data skipping. In this method, degree of variation of an image is calculated at first, and then this variation is used to compute a variation threshold. However, in this method, during the detection process, some additional memory has to be allocated in order to temporarily store the block variations, and then a threshold value is computed after the variations are suitably sorted; finally the blocks that are not selected as image data to be skipped in the frame are encoded. In compared with the present invention, in the method proposed in U.S. Pat. No. 6,560,370, not only the coding process is much more complicated, but the computation burden for detecting the image data to skip is also increased.
Additionally, in U.S. Pat. No. 6,192,148, there is disclosed yet another video coding method using image data skipping. In this method, sums of the absolute values of the prediction residuals between estimated motion and luminance, chrominance are compared in order to test the feasibility of block skipping. However, prior motion estimation is needed in this method, therefore in compared with the present invention the amount of operation that can be reduced in the said prior art technique is very limited.
Furthermore, in U.S. Pat. No. 6,993,078, there is disclosed yet another video coding method using image data skipping. This method is similar to the invention described in the aforementioned U.S. Pat. No. 6,192,148, where the computation of motion estimation is needed in both cases and then the feasibility of the block skipping is examined by using the sums of the absolute values of the prediction residuals between motion vectors and chrominance, luminance together with the maximum predicted absolute differences of chrominance, luminance. In compared with the present invention, the capability of the block skipping detection is restricted in the said method.
Furthermore, in U.S. Publication No. 2006/0164543 published on Jul. 27, 2006, there is disclosed another video loading method using image data skipping. The Zero prediction displacement and constant threshold of this method is limited the detecting function of the block to be skipped.
In order to improve the drawbacks in the aforementioned prior art, the present invention provide herewith a video coding method using image data skipping based on likelihood ratio testing. A likelihood ratio of block coding is computed for each partitioned data corresponding to the prediction displacements and then the likelihood ratio is used to dynamically adjust decision intervals so as to determine whether the block encoding has to be terminated; therefore the detection capability can be efficiently improved, and the computation burden, memory access and power consumption of a encoding device can be reduced so that the drawbacks existing in the prior art can be substantially improved.